Modern electronic products, including computers, consumer products such as digital cameras, digital video recorders and the like, and other products employ high-capacity storage devices to achieve high performance. Atomic resolution storage (ARS) technology represents an attractive option for satisfying the demand for storage in such products.
An ARS storage device typically includes electron field emitters that are arranged to write data to, or read data from, a large number of storage locations on a storage medium. The field emitters, sometimes alternatively referred to as “point emitters” or “probes,” are configured with sharp tips.
During operation of an ARS storage device, a predetermined potential difference is applied between a field emitter and a corresponding gate. An electron beam current is emitted from the sharp tip of the field emitter toward the surface of a storage medium. Writing data from a field emitter to a storage location on the storage medium is accomplished by temporarily increasing the power density of the electron beam current. The electron beam current with increased power density modifies the structural state of the surface of the storage medium that corresponds to the target storage location. Reading data from the storage location may be accomplished by observing the effect on the storage location that results from bombardment by an electron beam.
Another type of ARS storage device includes contact-based scanning probes that are used to read from and write to a storage medium. Each scanning probe has a tip that contacts the surface of the storage medium. Storage of data is based on perturbations (such as dents) created by the probe tip in the surface of the storage medium.
Defects in the storage medium of an ARS storage device can lead to read errors. Storage devices typically have some type of a failure recovery mechanism to recover certain types of read errors. Conventionally, in response to detecting a defective storage region, the failure recovery mechanism accesses predetermined information, such as information in a look-up table, to identify the location of a spare storage region storing data for defective storage regions. Once the spare storage region is identified, the probe of the ARS storage device is moved to the spare storage region. The process of detecting a defective storage region, identifying a spare storage region for the defective storage region, and moving the probe from the defective storage region to the spare storage region is relatively time consuming. Thus, whenever a defective storage region is encountered, an access time penalty is incurred, which slows down storage access.